Magnetic device



Dec. 18, 1962 G. M. sToUT ETAL 3,069,602

.MAGNETIC DEVICE Filed May 28, 1959 ,47m/@vers United States Patent G 3,069,602 MAGNETIC DEVICE Glenn M. Stout, 5605 Golden Valiey Road, and Fred W. Temple, 2407 Pleasant Ave. S., both of Minneapolis, Minn.

Filed May 2S, 1959, Ser. No. 816,627 Ciaims. (Cl. 317-465;

This invention relates to a magnetic circuit and further relates to specific applications of the magnetic circuit in such devices as relays and the like.

An object of our invention is the provision of a new and improved magnetic circuit which is of simple and inexpensive construction and is capable of producing results heretofore unknown.

Another object of our invention is the provision of a magnetic device employing a magnetic circuit of high reluctance wherein the magnetic-ilu); density of the circuit is not materially changed upon the opening of an air gap due to the movement of a part in the circuit.

A further object of our invention is the provision of a novel magnetic device employing a high reluctance magnetic circuit including a stator, and an armature which -is movable, and which may be either locked or moved from one position to another, dependent upon the amplitude of the signal or pulse applied to a variable source of magnetic flux in the circuit.

These and other objects and advantages of our invention will more fully appear from the following description made in connection with the accompanying drawings where like reference characters refer to the same or similar parts throughout the several views and in which:

FIG. l is a schematic diagram of the magnetic circuit employed in the magnetic device;

FIG. 2 is a schematic diagram of a variation of the circuit shown in FIG. l;

FIG. 3 is a schematic view of another variation of the magnetic circuit;

FIG. 4 is a schematic view showing still a further variation of the magnetic circuit;

FIG. 5 is a schematic diagram of a variation of the circuit shown in FIG. l;

FIG. 6 is an end elevation view of one form of relay employing the magnetic circuit of the present invention;

FIG. 7 is a longitudinal section of the relay shown in FIG. 6 and taken on a plane as indicated substantially at 6-6 in FIG. 6;

FIG. 8 is a somewhat diagrammatic plan View of still another type of relay employing the magnetic circuit;

FIG. 9 is a somewhat diagrammatic side elevation view ofthe relay shown in FIG. 8;

FIG. l0 is aperspective view of still another form of j relay employing the magnetic circuit; and certain portions of the rclayare broken away to show clarity of detail;

FIG. ll is a perspective View, partly broken away, and shown in section, of still another form of relay employing the magnetic circuit of the present invention.

One of the primary features of the present invention is the maintenance of an extremely high flux density between a stator and a movable armature, even though an air gap is opened between the stator and armature. In most applications, such as in relays or the like, the length of the air gap opened between the stator and armature is relatively small. In order to accomplish the maintenance of a substantially constant ilux density in the air gap, the present invention employs a high reluctance magnetic circuit. The magnetic circuit mav be worked out in any of a number of fashions hereinafter more fully set forth.

Another important feature of the present invention is concerned with the capability of the magnetic device in `response to the application thereto, of current pulses in ice similar directions, to cause the armature to move from one position to another, or to be locked in one position, depending upon the amplitude of the pulse of current applied. To Ythis end the magnetic device is provided with a high reluctance magnetic circuit including a stator having a source of magnetomotive force and a movable armature which also has a source of magnetomotive force. Preferably the source of magnetomotive force in the-stator has high reluctance so as to prevent demagnetization of this source when high amplitude signals are applied to the controllable source of magnetomotive force on the armature. It may be desirable in some instances to place the `high reluctance` source of magnetomotive force in the .movable armature. Several embodiments of magnetic circuits and relay constructions are shown in the drawings in connection with thesev several features of the present invention.

A simpiiiied diagrammatic sketch ofthe magnetic circuit embodying the present invention is shown in FIG. 1. The -magnetic circuit includes, as a source of magnetic flux,

.a ceramic permanent magnet 10 which .is shown in the shape of a rectangular block. The ceramic permanent magnet 10 is Vknown to persons .skilled in the art and is presently commonly sold under a number of various trademarks. The ceramic permanent magnet 10 is polarized so as to define opposite magnetic poles at spaced `surface portions thereof, and in FIG. l it is assumed that the magnet 10 has a north magnetic pole at the surface 11 and a south magnetic pole at the surface 12. Frequently, the ceramic permanent magnets such as the magnet 10, lare polarized ina direction through the thinnest dimension ofthe magnetic block and therefore the surface portions at which magnetic poles are defined have greater surface areas than the'other surfaces of the block.

' It is to be noted that the ceramic permanent magnet 10 has a permeability of the order of air and therefore has a high reluctance, and more specifically, the ceramic permanent magnets which have' been used in connection with the present invention have a permeability of 1.2 as compared with air which has a permeability of 1.0. yIt should further be noted that the ceramic permanent magnet 10 is an electrical insulator.

The magnetic circuit also includes magnetic flux pathconfining means for directing the magnetic flux in a conlined path between the magnetic poles of the magnet, and

said means includes a number of parts, 13, 14 and 15, all of which are constructed of magnetic material havinga permeability of the order of iron. It will be recognized A that the permeability of iron of the type frequently emp loyed in cores and armatures of magnetic devices is approximately 6,000." In the magnetic circuit shown in FIG. 1, the parts 13 and 15 engage in fixed relation the surfaces v11 and 12 of magnet 10 and are thereby magnetically coupled with the magnet and may be regarded as pole pieces, and the combined magnet 10 and pole pieces 13 and 15 may be regarded as a stator.' n The pole pieces 13 and 15 extend away from magnet 10 and at their tips are diminished in size to dei-lne surface portions or faces 16 and 17 of predetermined areas.

The part 14 of the magnetic circuit is, in the position shown, engaged at its surface portions or pole faces 18 and 19, with the surface portions 16 and 17 respectively of the pole pieces 13 and 15. The part 14, which may be regarded as an armature, may be separated from the pole pieces 13 and 15 such as into the dotted position A shown in FIG. l, so as to create small air gaps in the magnetic flux path between the opposed surfaces 16 and 18 and 17 and 19 of the pole pieces and armature respectively. Normally, the armature 14 has force exerted thereon in proportion to the number of lines of magnetic flux passing between the pole pieces and the armature at the opposed surfaces 16-19 thereof.

The use of this type of permanent magnet effectively increases the reluctance of the circuit by introducing an air gap into the magnetic circuit equal to the length of the magnet between the surfaces 11 and 12 thereof. It has been experienced that the magnetic liux density at the surfaces 16, 17, 18 and 19 (which is related to the force on the armature) is reduced upon opening of an air gap between the surfaces, only in relation to the proportion of the thickness of the ceramic magnet between the surfaces 11 and 12 thereof (and the total of the lengths of air gaps and the thickness of the ceramic magnet between the surfaces 12 and 12 thereof). For instance, if the length of the permanent magnet between the surfaces 11 and 12 thereof is 0.6 cm. and the armature is moved out of engagement with the pole pieces (from an air gap of zero) so that the total air gap in the magnetic ihlx circuit is 0.1 cm., the total magnetic iiux at the surfaces 16-19, which may be 2000 lines when the surfaces engage each other, is reduced only by the ratio of 0.6 to 0.7. it will be seen therefore, that the flux density in the air gap will remain extremely high particularly as compared to the situation which would exist if the circuit had low reluctance by employing a conventional iron magnet having a permeability of the order of A6000. The iiux density at the air gap changes in relation to the change AR in reluctance as compared with the overall circuit reluctance R.

The armature 14 is magnetically coupled with a coil 21 which is wound therearound and which, when connected to the source of direct current electrical potential, provides a variable source of magnetic iiux which controls the magnetic fiux in the armature 14. It will be recognized that if the current passes through the coil 21 in one direction, a north magnetic pole will be established at the surface 18 thereof and a south magnetic pole is established at the surface 19, and if the current in the winding is reversed, the polarities of the magnetic poles created are reversed. 1f the current in the coil produces north and south magnetic poles at the surfaces 18 and 19 respectively, the armature 14 and pole pieces 13 and 15 will repel each other due to the existence of north and south magnetic poles at the pole faces 16 and 17 relspectively. When, due to the repelling forces, air gaps between the opposed surfaces have been opened, the lchange AR of the circuit reluctance is small in relation to total circuit reluctance R, and therefore the magnetic iiux density in the air gap is not materially reduced. It will therefore be seen that the armature 14 will be moved by substantial force acting thereagainst after an air gap of substantial length has been opened.

It should be pointed out that in order to produce this snap action movement of the armature as previously described, it is only necessary to apply a single pulse of current to the coil 21. The pulse of current need only be suiiicient to create such a magnetomotive force as to create a magnetic field intensity at the surface portions 18 and 19 of the armature which approximately equals the magnetic field intensity at the surfaces 16 and 17 from the permanent magnet.

It will be recognized that there is a substantial amount of magnetic iiux leakage between the pole pieces 13 and 15, said leakage being indicated by the lines 22. The leakage path for the magnetic flux is usable advantageously in the following manner. It has been found that if the magnetic field intensity at the opposed surfaces 16, 17, A18 and 19 of the pole pieces and armature due to the magnetomotive force from the permanent magnet can be overcome by the magnetic field intensity from the coil 21, the armature 14 will lock up or remain stationary with respect to the pole pieces, regardless of the polarity of the vmagnetic field created by the current flowing in the coil 21. The ymagnetic flux from the armature passes into the ends of the pole pieces and then across the air gap as indicated at 23. In order to create the necessary conditions to allow the armature to lock up, all portions of the armature must have sufficient crosssectional area so as to carry, without saturating, sufiicient magnetic flux as to create a field intensity at the pole faces suliicient to overcome the magnetic field intensity from the permanent magnet, and the coil 21 must have sufficient current-carrying capacity to create the necessary magnetomotive force as to establish the required field intensity at the pole faces.

When the armature is to be locked up, a substantial quantity of current is passed through the coil 21 so as to suddenly establish an overpowering magnetic field in the armature 14 having a north magnetic pole at the surface 13 and a south magnetic pole at the surface 19 (or the polarity of the magnetic field could be reversed). The magnetic field created by current liowing in the coil 21 will have sufficient magnetomotive force as to create a magnetic field intensity at the faces 1S and 19 so as to overcome the magnetic field intensity at the end of the pole pieces due to the magnetomotive force of the permanent magnet. Because the magnetic iield intensity at the ends of the pole pieces has been overcome by the magnetic field from the coil, the armature and the pole pieces are subjected to attractive forces which cause the armature to be retained in engagement with the Isurfaces 16 and 17 of the pole pieces. The magnetic flux passes across the air gap at 23 to form the closed loop. rIhe low reluctance of the magnet 10 prevents demagnetization of the magnet.

Because the armature 14 can be caused to lock in relation to the pole pieces 13 and 15 by virtue of a pulse of current of exceedinly high magnitude applied into the coil, and because the armature will be repelled from the pole pieces if the pulse of current applied to the coil 21 has a somewhat smaller magnitude, it will be seen that the magnetic circuit acts as a pulse magnitude discriminator so as to operate at certain times in response to certain conditions and to fail to operate at other times in response to other conditions.

The form of the invention in FIG. 2 is substantially identical to the magnetic circuit shown in FIG. 1 with the exception that the permanent magnet 2S is magnetically coupled with the opposite end portions 26 and 27 of the armature 28. The pole pieces 29 and 30 are interconnected by a core 31 having a permeability of the order of iron and having the coil 32 magnetically coupled thereto by being wrapped therearound. In this arrangement it will be noted that the pole pieces 29 and 30 are of substantial length whereas the armature end portions 26 and 27 are relatively short and there will be substantially more leakage between the pole pieces 29 and 30 than between the opposite ends 26 and 27 of the armature and therefore in this arrangement it will be impossible to create suiiicient magnetomotive force from the coil so that the magnetic field intensity created by the coil at the ends of the pole pieces 29 and 30 will be sufficient to overcome the magnetic eld intensity from the permanent magnet 25 and therefore it will be impossible to lock the armature to the pole pieces.

It will be noted that the magnet-engaging shoe portions 26a and 27a of the opposite end portions 26 and 27 of the armature do not extend laterally outwardly beyond the confines of the permanent magnet and therefore there will not be sufiicient flux leakage through the air around the outside of the permanent magnet 25 as to permit the armature to lock with respect to the pole pieces 29 and 30.

The form of the invention shown in FIG. 3 is similar to that shown in FIGS. 2 and 1 and in this form of the invention, the ceramic permanent magnet 35 is engaged by shoes 36 and 37 forming portions of the armature end portions 38 and 39 respectively, and the shoes 36 and 37 project transversely outwardly and into relatively closely spaced relation with each other as at 36a and 37a respectively so as to permit a substantial leakage at flux as at 40 around the permanent magnet 35 and thereby permit the magnetic field intensity in the pole pieces 41 and 42 from the field created by the coil 43 to overcome the magnetic field intensity from the permanent magnet 35 and cause the armature to lock with respect to the pole pieces regardless of the direction of current flow through the coil 43. Again, in this form of the invention, when the source of current is applied to the coil 43 of somewhat lesser magnitude, repulsive forces are established at the ends of the pole pieces so as to produce relative movement between the armature and the pole pieces away from each other.

In the form of the invention shown in FIG. 4, the ceramic permanent magnet 45 is magnetically coupled with the armature end portions 46 and 47 by the shoes 46a and 47a which engage the opposite surfaces of the magnet 45. The pole pieces 48 and 49 are spaced from each other but held stationary with respect to each other and a movable permanent magnet 50 is magnetically coupled at its opposite magnetic field poles to the pole pieces 48 and 49 to provide a variable source of magnetomotive force and to create a magnetic field intensity at the ends of the pole pieces so as to either attract or repel the armature, depending upon the physical arrangement of the magnet 50 wtih respect to the pole pieces 48 and 49. The permanent magnet 50 might be employed alone and inserted between and removed from the pole pieces 48 and 49 and be physically reoriented in response to certain conditions so as to either cause the armature to move or 'to remain stationary; or in the alternative the permanent magnet 50 might be one of a number of permanent magnets moving along a predetermined course to 'pass'between thefpole pieces 48 and'49 and cause the armature to move,'dependent upon the orientation of the permanent magnets as they progress betweenthe pole pieces'48 and 49.

f The form of the inventionsh-own in FIG. 5 is similar to thatshown'inFlG. leircepting that the stator including the poley pieces 70`and 71, also include an electromagnet 72, the ends of the core of which are spaced at 73 and S74 from the pole pieces 71 and 70 to introduce a permanent air gap into the magnetic circuit and thereby 'cause the magnetic circuit to have a high permanent reluctance. The movable armature 75 has a coil 76 wound thereon to provide a controllable source .of magnetomotive vforcel in order to cause movement of the armature.

The formof the invention shownin FIGS; 6 and 7 comprises a. magnetically latching pulse-operated-relay employing the novel magnetic circuit hereinbefore described. VThe relay is indicated in general by numerall 52 and includes a rectangular block 53 of ceramic permanent magnet material withthe magnetic` eld thereof oriented through the ,thinnest dimension thereof to establish magnetic field poles of opposite polarities at the opposite surfaces 53er and 53b thereof. The magnetic circuit also includes a pair of pole pieces 54 and 55 which ,lie against the'surfaces 53a and 53h respectively of the permanent magnet 53 and are thereby magnetically .coupled therewith, and the magnetic circuit also includes -a movable armature 56 which engages the pole pieces 54 `and 55. The pole pieces 54 and 55 and the armature 56 are constructed of iron for conducting the magnetic flux path therethrough. l

The relay 52 is also provided with a framing structure for holding the pole pieces 54 and 55 and the armature 56 and the permanent magnet 53 in predetermined relation with respect to each other. The framing structure,

which is indicated in general by numeral 57 is constructed of non-magnetic material, and includes a pair of side plates 57a and-57b which overlie the pole pieces, and a pair of upright end plates 57a` and 57d which are formed iin interlittingrelation with respect to the side plates so as to be held in stationary condition thereby and which project upwardly from the side plates to provide a suitable mounting for the movable armature 56. The side plates are held together in `engagement with the pole pieces by suitable means such as cement or a bolt 57e which projects -through the ceramic permanent magnet 53 and through the pole pieces and frame side members 57a and 57b.

The armature 56 includes an elongate shaft 58 having diminished end portions 58a which are journalled for rotation in suitable bearing apertures 59 in the frame end members 57e and 57d respectively. The armature 56 also includes a pair of armature end members 60 and 61 aflixed on the shaft 58 and extending transversely outwardly therefrom. As best seen in FIG. 6, the armature end members 60 and 61 are oriented angularly with respect to each other an-d on shaft 58 for respectively engaging the upper edges and inner sides of the upwardly projecting arms or engaging portions 54a and 55a of the pole pieces 54 and 55 respectively. It will be seen that the armature end member 61 engages, over a substantial surface area, the upper edge of one of the arms 54a of pole piece 54, and the armature end member 6i) simultaneously engages, over a substantial surface area, the inner side of one ofthe upstanding arms 55a of the pole piece 55. It will further be seen that when the armature 56 is rotatably oscillated in a clockwise direction as viewed in FIG. 5, the armature end member 61 will engage one `of the arms 55a of pole piece 55 and the armature end member 60 will engage one of the arms 54a of the pole piece 54. It will thereby be seen that in either position of the armature 56 the magnetic flux path between the opposite magnetic field poles of the permanent magnet 53 is closed through the pole pieces and armature.

A variable source of magnetic ux or magnetomotive force is magnetically coupled with the armature and in the form shown, the source consists in a coil 62 of Wire wound on a spool 63 which has an open center 63a throughywhich passes the shaft 58. The spool 63 has a .plurality of endwise extending lugs 63b which project .through suitably provided mounting apertures 63e in the frame end member 57C and 57d respectively to support the spool with respect to the armature and to prevent rotation of the spool. The coil of wire 62 is connectible to a source of electric power as by the tabs 62a. It may be desirable to superimpose a plurality of operating coils or a read-out coil on the coil 62. The coil 62 might, on the alternative, be Wound directly on the shaft 58 and be electrically connected through flexible leads. i

The relay may also have a plurality of substantially stationary contacts 64 and a plurality of movable contacts 65 for engagement with one or another of the statronary contacts 64. The contacts 64 and 65 are secured to the frame structure as by screws 66 and are insulated from. each other and from the frame structure by insulatmg strips`67. Means are provided for connecting the movable contacts 65 with the movable armature 56 so.. as to produce movement of the movable contacts 65 when the armature 56 is moved fromK one position to another. In the form shown, each of the movable contacts 65 has `a projection 65a on Ithe upper end thereof which 1s connected to a crossbar 68 which is moved in an endwlse direction for operating the contacts 65 by means of an upwardly projecting finger 69 from the armature end member and projecting through a suitably provided bearmg aperture (not shown) inthe bar 68. It will ybe seen that as the armature 56 is `oscillated from one position to another, the movable contacts 65 will first engage one of the stationary contacts adjacent thereto and then the other stationary Contact. It will be recognized that other other .contact arrangements might be used, such as commutatmg.

The comparability between the magnetic circuit of relay 52 and the magnetic circuit shown diagrammatically in FIG. 1 Will be recognized. The ceramic permanent magnet 53, with its permeability of 1.2, effectively provides an air gap in the magnetic circuit equal to the thickness of the magnet S3, or the distance between the pole pieces S4 and 55. Therefore, the total flux passing between the pole piece arm 54a and armature end member 61 and the pole piece arm 55a and -the armature end member 60 is reduced, upon the opening of an air gap when the armature is moved, by the proportion of the increase in the air gap length as compared with the total air gap length in the circuit (which includes the thickness of the magnet 53 plus the air gaps between the armature end members and the pole piece arms).

When the relay 52 is to be operated, a pulse of current is applied to the coil 62 with such a magnitude duration and polarity as lto cause production of a magnetic field in the armature with such field intensity at the armature end members as to cause a repelling force to be exerted against the armature end members, which causes the armature to move. It should be recognized that the flux density in the air gap at 55a and 61 is increased and is decreased due to the magnetomotive force of the coil. Therefore, the repelling force exerted on the armature (which is proportional to the product of the magnetic ux density of the permanent magnet and the coil iiux) is not materially decreased as compared with the force exerted on the armature just prior to the opening of the air gap. The armature will thereby be rapidly impelled away from the pole piece arms previously engaged and as this air gap is opening, the air gap between the armature end members and the other pole piece arms is continuously closing. The repelling force exerted on the armature is sufficient to cause rapid and positive swinging o-f the armature into a position where the attractive forces between tne armature end members and pole pieces (at the air gaps which are closing) adds to the repelling force. As the armature end member 61 approaches the pole piece arm 55a, and as the armature end member 60 approaches the pole piece arm 54a the magnetic ux densities in the air gap due to the magnetic field intensities in the armature end members and pole pieces respectively, may be added to each other and the attractive forces swing the armature end members into positive engagement with the pole piece arms with a considerable impact. It will therefore be seen that as the armature end members successively engage and seat against the pole piece arms in successive operatic-n of the relay, the surfaces of the pole pieeearms and of the armature end members are matched by the continuous impacting so as to engage each other over the maximum possible surface area. This action may be regarded as a continuous peening of each of the armature end members and pole piece arms by each other.

It will be recognized that as the armature swings from one position to the other the leaf springs of the movable and substantially stationary contacts are exed in such a manner that the spring pressure tends to pull the armature end members off the pole piece arms. In addition, vibration of the entire relay, shock forces and contact bounce may also tend to move the armature. However, it should be noted that the improved characteristics of the magnetic circuit which prevent any substantial decreasing of the magnetic ux intensity at the opposed surfaces of the armature end members and pole piece arms cause the armature to be securely held in the desired position (in absence of a pulse on the coil) so that the relay resists such iniiuences as contact bounce, vibration and shock forces without any substantial possibility that the armature or contacts will be allowed to operate erroneously. The relay has the further advantage of having its armature locked in a stationary position when the relay is in disuse, such as during shipping of the relay from the manufacturer to the user. Because the armature is effectively locked in position, substantially no damage can result due to shock forces and the like during the shipment of the relay.

With regard to the magnitude and duration of the pulse of current necessary to be applied to the coil in order to produce operation of the relay and shifting of the armature, it should be pointed out that the coil may be of extremely low impedance and that the pulse may be extremely short. Therefore only a fraction of a wattsecond is consumed in each operation, which permits the relay to be completely confined within a small enclosure with no provision made for dissipation of heat. Because the pulse of current is of extremely short duration, the relay may be safely operated at many times the minimum voltage required to cause operation of the relay and therefore the voltage of the electric current source applied to the coil may be kept at a high level so that small variations in the voltage due to changes in voltage of the supply are ineffective to cause faulty operation of the relay. As an example, a test relay with a 13 ohm coil operated and completed shifting of its contacts approximately 8 milliseconds after application of l2 volts D.C.; and also operated reliably and completed shifting of its contacts approximately 4 milliseconds after application of a 25 volt D.C. pulse; and a relay with this same 13 ohm coil was successfully and reliably operated by a discharge pulse from a 3 microfarad condenser charged to l2() volts D.C.

It should be recognized that if a second read-out coil is superimposed on the coil 62 or otherwise magnetically coupled with the armature, the position or state of the magnetically detented armature may be determined by supplying the read-out coil with a current pulse of predetermined polarity. Depending upon the state or position of the armature, the read-out coil will exhibit a relatively high or a relatively low inductive reactance. On the alternative, a pair of read-out coils may be employed, both magnetically coupled with the armature. A pulse of current may be applied to one coil, and the output pulse from the other coil will have relatively high or relatively low amplitude, depending upon whether the armature is in one position or the other.

The magnetic circuit described in connection with FIG. l is also embodied in the form of relay which is shown somewhat diagrammatically in FIGS. 8 and 9 and which is indicated in general by numeral 82. The relay includes a ceramic permanent magnet 83 against which the pole pieces 84 and 85' lie at the opposite magnetic field poles of the magnet, and may be held in this predetermined relation by the frame means which is indicated in general by numeral S6 and is shown in dotted lines. An armature, indicated in general by numeral 87 is provided with a longitudinally slidable elongate shaft 88 having transversely extending end members 89 on the opposite ends thereof and depending therefrom for movement between and engagement with inwardly extending pole piece arms 84a, 84h, 85a and 85h. The armature, in one position thereof, will engage the pole piece arms a and S41) and in the other longitudinally shifted position will engage the pole piece arms SSb and 84a. Suitable bearing means 86a are provided on the frame means to guide the armature in its longitudinal movement. Contacts 90 may be provided in each end of the relay to be operated by longitudinal shifting movement of the armature. The relay 82, which employs the magnetic circuit previously described in connection with FIG. 1 has substantially the same operating characteristics of those already described except that the armature has a longitudinal shifting movement instead of a swinging movement.

The form of the relay shown in FIG. 10 is substantially identical to that shown in FIGS. 6 and 7 except for certain modifications. In this form of the relay, which is indicated in general by numeral 91, the pole pieces which overlie the opposite surfaces of the ceramic permanent magnet 92 are each split into two end sections 93a and 93h which are spaced from each other in edge-to-edge relation to be electrically insulated from each other and are separated by an insulating strip 94 which may be constructed of fiber or the like. Each of the pole piece end portions has an armature-engaging arm 95, and as previously described, the armature 96 has the end members 97 which are rotatably oscillatable for respectively and simultaneously engaging pole piece arms of opposite polarity. The end portions 93a and 93b of the pole pieces, which are electrically insulated from each other, may have means for connection into an electric circuit such as the tabs 98 which are formed integrally of or soldered to the arms 95. The coil 99 encompasses and is magnetically coupled with the armature shaft. It will be noted that when the armature end members engage one pair of pole piece arms 9S, an electrical connection is provided therebetween, and when the armature is shifted into the other position, the other set of pole piece end portions are interconnected. It will therefore be seen that contacts of the type shown in FIGS. 6 and 7 may be eliminated. In this relay 91, electrical arcing at the points of engagement between the armature and the pole piece end members is substantially suppressed by the existence of the magnetic ux in the air gap between the parts. As previously described, the armature endmembers engage the pole piece arms with a considerable impact to effect apeening action. It should be noted that this peening action causes flattening .of any .minute nodules or the like which may be, produced as a result of electrical arcing between the armature and pole piece arms.

All of the relays shown in FIGS. 6-11 have the capabilities of being locked'up in response to a current applied to the coil of such a'polarity that a magnetic field is created at the armature end members in opposition to the magnetic field from the permanent magnet and lthe current is of such a magnitude as to cause the field intensities from the coil to overcome, at the pole piece arms, the magnetic field from the permanent magnet. This was described in connection with the magnetic circuit shown in FIG. l. This locking up feature is describedparticularly in connection with relay 91 shown in FIG. 10 because in this relay the concept can be well understood without theaction of the springs (on the other .forms of therelay) becoming involved. The locking up feature is common to the other relays with the springs but it is more easily understood with regard to this particular relay. The coil 99 must have such a currentcarrying capacity as to create in the armature, a magnetic -field having such magnetomotive force that the magnetic field intensity-at the pole-engaging armature end members is substantially greater than the field intensity at the pole piece arms 95 from the magnetic field of the permanent magnet. The path of the magnetic flux from the coil is through the armature end members to the pole piece arms 95 and then by leakage ilux across the air gap to the other pole piece arm 95 and then back through the pole piece to the other end of the armature. As an example, if -the permanent magnet 92 normally creates (without any current in the coil 99) a magnetic field intensity at the pole piece arms 95 of approximately sixtytwo Oerstads which causes substantial magnetic saturation of the armature, the armature would be locked up and prevented from moving if the coil 99 produces a magnetic field intensity of approximately 128 Oerstads at the pole piece arm-engaging surfaces of the armature end members 97. Under this condition the armature end members are attracted to the pole piece arms because the pole piece arms actually comprise a portion of the magnetic circuit carrying the lines of flux from the coil. This is in contrast to the results when the current in the coil 99 is of such a magnitude as to create a magnetic field intensity at the armature end members which is substantially equal to the magnetic field intensity at the pole piece arms from the permanent magnet, at which time a repelling force is created between the armature and the pole pieces and causes the armature to shift to the other position.

The magnetic circuit described in FIG. 1 is also embodied in the form of the relay shown somewhat diagrammatically in FIG. 11, wherein the frame structure is eliminated but will be substantially similar to that shown in FIGS. 6 and 7. The relay of FIG. 11 which is indicated in general by numeral includes a pair of pole pieces 101 which engage the ends of the iron cores 102 of coils 103. The iron cores 102 have air gaps between the ends thereof to permit one core to shunt all the magnetic flux when only the other coil is energized. The armature, which is indicated in general by numeral 104 has a shaft 105 which is rotatable about a longitudinal axis and which has thereon armature end members 106 identical to those previously described and engaging the pole piece arms 107 of opposite polarities. The shaft 105 is discontinuous at its central portion and has thereon a pair of engaging shoes 108 which engage the opposite ends of a ceramic permanent magnet 109 which, in the form shown, is generally cylindrically shaped and has a central opening to receive the stub ends of the shaft end portions. The operation of this form of the invention is substantially 'similar to those already described. When the coils create a vmagnetic field intensity at the pole piece arms sufficient to cause a repelling action, the armature will shift to the other position thereof with substantially the same movement and operating characteristics of the other forms of the relay. The coils 103 maybe designed so as to individually produce suflcient magnetomotive force as to cause operation of the relay, or on the alternative, the coils 103 may be designed so as to necessitate energization of both of the coils befor the relay will operate.

With regard to the operating characteristics of all of the forms of the relay herein disclosed, another important operating characteristic should be mentioned. Reference is specifically made for purposes of this explanation to relay 52 shown in FIGS. 6 and 7, but it should be pointed out that the characteris-tics are common to all of therel'ays. When a pulse of currentis appliedvto the 'coil'6 2,'repelling`forces are exerted on thearmature end members 60 and 61 which causes rotationjofthe armatu're in a clockwisedirection. It has been experienced 'that as the armature end'members approachthe other pole piece arms, the attracting forces are substantially greater than the previously mentioned repelling' forces. This is apparently due to the fact that the opposite polarities of the magnetic fields which produce the initial repelling cause a decrease in the flux density at the air gaps as the armature starts to move. Conversely, the magnetic fields from the coil and from the permanent magnet have an additive effect during the final phases of the movement of the armature, at which time the ux density is materially increased in the closing air gaps between the armature end members and the pole piece arms. The phenomenon is useful in operating spring contacts during the final phases of the armature movement.

It will, of course, be understood that various changes may be made in the form, detail, arrangement and proportion of the parts without departing from the scope of our invention which consists of the matter described herein and set forth in the appended claims.

What we claim is:

l. A magnetic device comprising, in combination, a magnetic circuit including means for changing the reluctance thereof by an incremental amount AR, a source of magnetomotive force in said circuit for creating flux therein, said magnetic circuit further including means for making its total reluctance R of a high value relative to the value of the incremental reluctance change AR.

2. A magnetic device comprising, in combination, a magnetic circuit including two relatively movable parts positionable to open and close an air gap in the circuit, a source of magnetomotive force in said circuit, said circuit having a total reluctance when the air gap is closed which is several times greater than the reluctance which is added to the circuit when the air gap is opened, whereby 11 the flux in said circuit does not change appreciably as the air gap `is opened and closed.

3. A magnetic device comprising, in combination, a magnetic circuit including two movable parts having a permeability greater than air and relatively movable to open and close an air gap in the circuit, a source of magnetomotive force in said circuit for establishing magnetic ux therein, said circuit having a total reluctance when said air gap is closed which is relatively high in proportion to the reluctance added to the circuit when the air gap is opened, whereby the ux in said circuit does not change appreciably as the air gap is opened and closed.

4. A magnetic device comprising, in combination, 4a magnetic circuit having a permanent air gap therein to establish high total reluctance, and said circuit also having two parts relatively movable with respect to each other to increase and decrease the total air gap in the circuit by an amount less than said permanent air gap, and a source of magnetomotive force in said circuit for establishing magnetic ux therein, whereby the ux in said circuit does not change appreciably as the air gap is opened and closed. I

` 5. A magnetic device comprising, in combination, a normally closed magnetic circuit including two relatively movable parts positionable to open and close an air gap in the circuit, a source of magnetomotive force in said circuit for establishing magnetic ilux therein, said closed magnetic circuit having sufficient length and suiciently low permeability to create a high total reluctance which is several times greater than the reluctance which is added to the circuit when the air gap is opened, whereby the flux in said circuits is not appreciably changed as the air gap is opened and closed.

6. A magnetic device comprising, in combination, a magnetic circuit including means for changing the reluctance thereof by an incremental amount AR, and excitable coil magnetically coupled with said circuit for establishing magnetic flux therein, and said magnetic circuit further including means for making its reluctance R of a high value relative to the value of the incremental reluctance change AR.

7. A magnetic device comprising, in combination, a magnetic circuit including means for changing the reluctance thereof by an incremental amount AR, a permanent magnet in said circuit for establishing magnetic flux therein, said magnetic circuit having a total reluctance R of a high value and several times greater than the value ofthe incremental reluctance change AR.

8. A magnetic device comprising, in combination, a magnetic circuit including means for changing the reluctance thereof by an incremental amount AR, a permanent magnet in said -circuit for establishing magnetic iiux therein, said permanent magnet being constructed of low permeability material for making the total reluctance R of the circuit a high value relative to the value of the incremental reluctance change AR.

9. In a magnetic device, the combination comprising a stator part and an armature part forming a magnetic circuit, means mounting said stator and armature parts for relative movement to open and close an air gap therebetween, a rst source of magnetomotive force in one of said parts, means in said circuit having a high reluctance relative to said air gap when the latter is opened, a second controllable source of magnetomotivc force in the other of said parts, whereby an abrupt increase in the magnetomotive force of the second source opposing said first source locks said parts together due to leakage of iiux around said high reluctance means.

l0. In a magnetic device, the combination comprising a magnetic circuit including a stator part and an armature part, means mounting said stator and armature parts for relative movement to open an air gap therebetween, a first controllable source of magnetomotive force in one o f said parts, means in the other of said parts providing a second source of magnetomotive force and providing reluctance which is high relative to said air gtp when the latter is open, said last mentioned part being constructed to cause flux opposing the second source to shunt through air and around said high reluctance means, whereby to permit locking of the parts by an abrupt increase in the magnetomotive force of said first controllable source in opposition to said second source.

References Cited in the tile of this patent UNHED STATES PATENTS 1,427,367 Fortesque Aug. 29, 1922 1,534,753 Watson Apr. 21, 1925 2,738,451 Bachi et al. Mar. 13, 1952 2,869,050 Van Urk. et al. Jan. 13, 1959 FOREIGN PATENTS 714,364 Germany Nov. 27, 1941 

